Lymphocytopenia, or lymphopenia, is the condition of having an abnormally low level of lymphocytes in the blood. Lymphocytes are a white blood cell with important functions in the immune system. The opposite is lymphocytosis, which refers to an excessive level of lymphocytes.
Lymphocytopenia can be caused by various types of chemotherapy, such as with cytotoxic agents or immunosuppressive drugs. Some malignancies in the bone marrow also cause lymphocytopenia.
People exposed to large doses of radiation, such as those involved with Chernobyl, can have severe lymphocytopenia.
A decreased number of certain types of lymphocytes, notably T cells, is a characteristic of AIDS.
Idiopathic CD4+ lymphocytopenia is the condition of having an abnormally low level of CD4+ T-cells. It has no known cause and is not associated with AIDS or any known infectious agent such as HIV or HTLV. It is associated with higher risks of opportunistic infections and cancer.
Lymphocytopenia may be present as part of a pancytopenia, when the total numbers of all types of blood cells are reduced. This can occur in marrow failure.
Lymphocytopenia is diagnosed from the results of a complete blood count. In adults, a lymphocyte level below 1,500 cells/microliter is diagnostic, and in children, a lymphocyte level below 3,000 cells/microliter is diagnostic.
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Lymphocytopenia that is caused by infections tends to resolve once the infection has cleared. Patients with idiopathic CD4+ lymphocytopenia may have either abnormally low but stable CD4+ cell counts, or abnormally low and progressively falling CD4+ cell counts; the latter condition is terminal.
^ D K Smith, J J Neal, and S D Holmberg. "Unexplained opportunistic infections and CD4+ T-lymphocytopenia without HIV infection. An investigation of cases in the United States". The New England Journal of Medicine328 (6): 429-431. PMID 8093633.
^ D D Ho, Y Cao, T Zhu, C Farthing, N Wang, G Gu, R T Schooley, and E S Daar (1993-02-11). "Idiopathic CD4+ T-lymphocytopenia — immunodeficiency without evidence of HIV infection". The New England Journal of Medicine328 (6): 386-392. PMID 8093634.
^ Thomas J Spira, Bonnie M Jones, Janet Nicholson, Renu B Lal, Thomas Rowe, Alison C Mawle, Carl B Lauter, Jonas A Shulman, and Roberta A Monson (1993-02-11). "Idiopathic CD4+ T-Lymphocytopenia — An Analysis of Five Patients with Unexplained Opportunistic Infections". The New England Journal of Medicine328 (6): 386-392. PMID 8093635.
^ W L Ng, C M Chu, A K L Wu, V C C Cheng, K Y Yuen. "Lymphopenia at presentation is associated with increased risk of infections in patients with systemic lupus erythematosus". Quarterly Journal of Medicine99 (1): 37-47. doi:10.1093/qjmed/hci155.